The present invention relates to apparatus and methods for winding textile yarn or the like to form a yarn package and, more particularly, to apparatus and methods for high speed precision cross-winding by traversingly moving a yarn along a rotating package core for cross-winding of the yarn thereon.
A variety of conventional apparatus of this type are available, such devices typically utilizing a rotatable spindle for supporting and rotating the package core, and one or more moving belts, chains or the like carrying yarn engaging elements for traversingly moving yarn longitudinally along the rotating package core, the belts, chains, or the like in a number of such devices being arranged so as to have two oppositely moving operational spans extending along the package. While all or most such devices may be successfully operated to varying extents, significant limitations exist in such devices with respect to the maximum package size which can be uniformly and symmetrically built or the speed at which the spindle and traverse mechanisms can be effectively operated.
In this regard, it has been discovered that two constructional features of yarn winding apparatus of this type, specifically, the orientation of the operational spans of the belt or belts of the winding apparatus both with respect to each other and with respect to the package itself, and the manner and means of handling the reversal transfer of the yarn between the operational spans of the belt arrangement, have a substantial effect on the symmetrical building of the yarn package and, in particular, on the formation of the ends of the package where the direction of movement of the yarn along the package is reversed. It is of particular importance that the reversal at each end of the yarn package of the direction of yarn traversal be consistently accomplished as precisely and identically as possible so that the ends of the yarn package will be built symmetrically with respect to each other. Moreover, it is additionally important that the reversals at each package end be accomplished at essentially equal spacings from the package and that the reversal spacing be within an optimum range which is neither too great nor too small since both extremely quick and slow, extended reversals can have deleterious effects upon uniform package construction. For example, where the yarn being wound is engaged during reversal and reversal is effected at a significant spacing from the package, a greater number of yarn wraps per unit length of the package are placed thereon at the ends thereof than are placed at the center of the package, causing tension and density variations in the package along its length and, in some cases, breakdown of the package ends. On the other hand, the reversal of the traversal direction of the yarn at a very close spacing from the package, and thereby very quickly, will cause the yarn to be laid on the package with a sharp angular bend therein at the point of reversal which bend will be overcome by the normal tension and twist in the yarn causing it to shift and assume a minimum curvature on the package, thereby also affecting the integrity of the construction of the package ends.
Typically the means utilized in prior art devices to effect the above-described reversal transfer between the operational spans of the belt arrangement comprises stationary cams for engaging and guiding the yarn between the spans by sliding of the yarn on the cams, examples of such being illustrated in Horwood U.S. Pat. No. 3,294,327 and Beckwith U.S. Pat. No. 3,333,782. A variation of this type of yarn camming arrangement utilizing a freely rotatable cam disc disposed between the two operational spans is disclosed in Ueda U.S. Pat. No. 3,620,464. Such cam-type reversal arrangements, while generally effective for their intended purpose, suffer from several drawbacks which render winding devices utilizing this type of reversal arrangement less desirable. Initially, a cam-type reversal assembly provides no means of positively engaging the yarn during reversal. Accordingly, any factor tending to cause variations between individual reversal operations in the sliding contact between the yarn being wound and the cams effecting reversal, such as tension, friction, etc., will necessarily cause variations from reversal to reversal in both the specific location at which removal of the yarn is effected from the belt span carrying it and the specific location of the reversal transfer of the yarn to the other belt span, thereby resulting in variations in the symmetry and uniformity of construction of the yarn package and effectively limiting the maximum package size which can be built. Such variations as the coefficients of friction are common, resulting, among other things, from oil on the yarn being wound, tension variations in the yarn along the length thereof along the yarn feed path, yarn flutter and vibration along the yarn feed path, and the accumulation of dust and fly on the belt or belts or on the yarn cams. As a result, yarn winding devices utilizing such cam-type reversal arrangements are generally unacceptable for winding relatively large yarn packages. Moreover, the fluttering and vibrating along the yarn feed path of the yarn being wound and the variation in tension of the yarn along its length sometimes additionally result in insufficient contact between the yarn being wound and the cams to insure effective sliding of the yarn along the cam surface for reversal resulting in failure of the reversal operation. Finally, such cam-type reversal arrangements provide no means of maintaining tension on the yarn being wound during the reversals and, therefore, there occurs a release or collapse of yarn tension at each reversal when the yarn is removed by the cams from the moving belt or belts of such winding devices, such tension collapse causing tension variations between the yarn wound about the center of the package and the yarn wound about the package ends which results in a non-symmetrical package having inferior package flanks.
In a number of prior art devices the operational spans of the belt or belts thereof are oriented in spaced parallel relation along the path along which the yarn is delivered to the package, examples of this construction being found in the above-referenced Ueda patent and in Rogers U.S. Pat. No. 3,981,458, Ballard U.S. Pat. No. 2,662,695, and Allen U.S. Pat. No. 1,170,212. In other prior art devices, the operational belt spans extend in spaced parallel planes oriented generally perpendicularly with respect to the yarn path, the spans being oriented in their respective planes in crossing relation when viewed in the direction of yarn feeding, this arrangement being disclosed in the above-referenced Beckwith and Horwood patents, and in Goodhue U.S. Pat. No. 3,565,359, and Burdge U.S. Pat. No. 3,586,251. In each of the above types of belt arrangement and in all of the above patents, the two operational spans of the belt assembly are spaced along the yarn path thereof, whereby one of the operational spans is necessarily closer to the yarn package along the entire operational length of the span than is the other span. As a result, reversal is effected at one end of the package by transferring the yarn from the span closest to the package to the other span which is spaced a greater distance from the package, while at the other end of the package reversal is effected by transferring the yarn from the span spaced the greater distance from the package to the closest span. A relatively slower, more extended reversal is thus effected in the former instance with the reversal in the latter instance being relatively quicker, this differing treatment of the yarn at opposite ends of the package resulting in further variations in the symmetry and uniformity of the package ends.
In contrast, the present invention provides a novel apparatus and method for winding yarn by cooperatively traversingly moving a yarn along a yarn package and positively engaging the yarn at the ends of the package to effect precise and relatively quick reversals of the direction of traversing movement of the yarn in an identical manner at each end of the yarn package to maintain the number of yarn wraps per unit length of the yarn package essentially uniform along the entire package length and thereby permit the building of uniform and symmetrical yarn packages at high operational speeds.
Necessarily interrelated with the yarn traversing and reversing assemblies of yarn winding machines and the like with regard to the symmetrical building of yarn packages is the driving system in such devices for rotating the spindle and moving the belt, belts, chains or the like. It is known in the art of cross-winding yarn to form a yarn package that the yarn winding angle, i.e. the angle at which the yarn is laid on the package with respect to the package axis, must be maintained within an acceptable range to provide stability and symmetry to the package. For example, if the yarn winding angle is too steep with respect to the package axis, the yarn will tend to fall or "sluff" off the package ends. In conventional devices, a single drive motor is normally utilized to effect rotation of the spindle and longitudinal movement of the belt arrangement. Since the yarn being wound is normally fed to the winding machine at a generally constant speed, such devices are conventionally mechanically arranged to gradually and continually decrease the rotational speed of the spindle as the diameter of the package increases during the building thereof to maintain the surface speed of the yarn package generally constant in conjunction with the generally constant rate of feeding of the yarn. As a result of the driving arrangement, the longitudinal speed of movement of the belt arrangement is necessarily reduced gradually and continually also, thereby maintaining constant the ratio between the longitudinal speed of movement of the belt arrangement and the rotational speed of the spindle. The number of yarn wraps per unit axial length of package thus remains constant throughout the building of the package, accordingly causing the yarn winding angle to gradually increase and approach 90 degrees as the package diameter increases. Inasmuch as the minimum and maximum acceptable yarn winding angles are relatively fixed, it is apparent that the maximum increment of package diameter which can be built utilizing such a drive system is limited.
In Osborne U.S. Pat. No. 2,652,987, it is proposed to reduce the rotational speed of the spindle in steps as the package builds to produce a stepped reduction in the ratio between the spindle rotational speed and the speed of traversing movement of the yarn, thereby periodically reducing the number of yarn wraps per unit length of package to accordingly reduce the yarn winding angle. While this arrangement may effectively maintain the yarn winding angle within acceptable limits, since the spindle rotational speed is varied in steps only and remains constant during each step the surface of the package is in no way regulated and therefor gradually increases during each step. As a result, this arrangement would be wholly unacceptable for use in any winding operation where a selected yarn characteristic or yarn feeding condition is to be controlled by controlling the surface speed of the package during the winding operation in relation to the characteristic or condition. An example of a winding operation requiring such control is the winding of yarn or filamentary material delivered to the winding apparatus from an extruder. In such a situation, the yarn take-up speed of the package must be maintained constant to insure uniform yarn characteristics along the entire length of the yarn. Any significant increases of the surface speed of the yarn package during winding would result in the gradual increase in the tensioning of the yarn, and thereby effect essentially a drawing operation possibly causing yarn breakage, weak or thin spots in the yarn, and produce a yarn of gradually increasing denier along the length thereof.
In contrast, the present invention provides a novel apparatus and method for winding yarn packages of relatively large diameter by maintaining the yarn winding angle within acceptable limits throughout the winding operation by periodically changing the ratio between the rotational speed of the spindle and the speed of traversing movement of the yarn, while also controlling a selected yarn characteristic or yarn feeding condition by controlling the surface speed of the yarn package in relation to the characteristic or condition.